1. Field of the Invention
The present invention details a class of ethers comprising at least two lactam rings, which may be the same or different. The ethers may be symmetrical or asymmetrical depending on the reactants, reaction, and/or reaction conditions. One preferred ether is bis-N-ethyl pyrrolidone ether. This and other ethers find useful service in the personal care, performance chemicals, and pharmaceutical arts, where they may serve as solvents, solubility aides, freezing point depressors, dispersing agents, reaction fluids, and cleaning agents.
2. Description of Related Art
There exists a great commercial need for fluids with advanced, multi-functional properties for application in performance chemicals, personal care, and pharmaceutical compositions and uses. Such fluids find utility as solvents, solubilizers, cleaning agents, extraction fluids, absorbing agent, heat transfer fluids, and dispersing fluids, among many other uses. Known fluids in these application areas often exhibit undesirable characteristics. For example, chlorinated hydrocarbons display excellent grease-cuffing ability, but many have harmful toxicological profiles which limits or excludes there use, for example, in personal care compositions. In other cases an effective cleaning fluid is not water soluble, which may rule out its use in water-based applications, e.g., for household or industrial hard surface cleaning, or laundry. It may be the case that to meet toxicological, environmental, and other considerations that such fluids end up having suboptimal properties, like limited ranges in freezing/boiling point or solvency, or solubility profiles.
The current invention discloses lactam compounds and describes their compositions and uses. One preferred compound is bis-N-ethyl pyrrolidone ether.
An early disclosure of bis-N-ethyl pyrrolidone ether is provided in an article by Reppe and Mitarbeiter (1955), which teaches its sodium-catalyzed synthesis from pyrrolidone and dichlorodiethyl ether. A 50 mole percent yield of bis-N-ethyl pyrrolidone ether was reported.
Shostakovskii, et al. (1961) esterified N-hydroxyethyl pyrrolidone with the chlorides of acetic, propionic, butyric, valerianic, and caproic acids. Upon distillation of the esters they identified bis-N-ethyl pyrrolidone ether, bis-N-ethyl piperidone ether, and bis-N-ethyl caprolactam ether.
A related compound is N-ethyl-2-pyrrolidone, which is discussed in WO 2005/0900447 as a solvent, diluent, extraction agent, cleaning agent, degreasing agent, absorption agent, and/or dispersion agent, especially as a replacement for N-methylpyrrolidone.
Also related is N-methylpyrrolidone, also referred to as NMP and offered into commercial sale by International Specialty Products as M-Pyrol®. NMP publications include the following 18 publications by the BASF Corporation, each of which is incorporated in its entirety be reference:    The brochure “Formulating paint strippers with N-methylpyrrolidone,” BASF Corporation, Chemical Intermediates, 1990, USA,    Walsh, W. C., “Removal of rosin- and resin-based solder flux from electronic assemblies with N-methylpyrrolidone/water mixtures,”    Walsh, W. C., “Degreasing and solvent regeneration in metal parts, cleaning using N-methylpyrrolidone,” e.g.: http://es.epa.gov/p2pubs/oaic/301.html,    Walsh, W. C., “Surface Tension Modification of NMP based Paint Strippers,”    Walsh, W. C., “N-methylpyrrolidone (NMP technical tips), removal of paints and coatings from NMP-soluble plastics,”    Walsh, W. C. (1991), “Surface tension modification of NMP-based paint strippers,” in Reducing Risk in Paint Stripping, Washington D.C., 12-13 Feb. 1991, pp. 177-184, Economics and Technology Division; Office of Toxic Substances; United States Environmental Protection Agency, Washington D.C., 1991,    Walsh, W. C., “N-methylpyrrolidone (NMP Technical Tips), Maintenance Cleaning of Aircraft Ball Bearing Assemblies,”    Walsh, W. C., “N-methylpyrrolidone (NMP Technical Tips); Cleaning of a Chlorinated Paraffin/Metal Stearate Based Drawing Compound Off of 1000 Ft. Long Coils of 0.25 inch, 316 Stainless Steel Tubing,”    Walsh, W. C., “N-methylpyrrolidone (NMP Technical Tips), Chemical Warfare Resistant Coatings (CARC), Removal From Metal Surfaces,”    Walsh, W. C., W. Monahan and M. Waidrop, “Reflux Cleaning of Large Reactors with N-methylpyrrolidone (NMP),”    Walsh, W. C., “Replacement of MEK with N-methylpyrrolidone (NMP) in coatings plant resin clean-up operation,”    Walsh, W. C., “N-methylpyrrolidone (NMP) technical tips, removal of polyurethane/polyurea residue from the interior surfaces of a batch reactor vessel,”    Walsh, W. C., “N-methylpyrrolidone-cleaning applications in the urethane manufacturing and processing industries,”    M. W. Waldrop and Walsh, W. C., “Modification of a vapor degreasing machine for immersion cleaning using N-methylpyrrolidone,”    Walsh, W. C., “Removal of N-methylpyrrolidone from metal parts using a centrifugal dryer,”    Walsh, W. C., et al., “A process to vacuum vapor degrease metal parts with N-methyl pyrrolidone,” http://es.epa.gov/techpubs/3/15413.html,    Walsh, W. C., et al., “Removal of N-methylpyrrolidone (NMP) from industrial plant exhaust air with a packed column scrubber,”    Walsh, W. C., et al., “A process to vacuum vapor degrease metal parts with N-methylpyrrolidone,” 1997, CA Abstract No. 127:7688,    Walsh, W. C., “N-methylpyrrolidone (NMP technical tips), reclaiming or recycling of NMP,” and    “Electrical insulation—from wire enamel to enameled wire,” 1 Beck Information, July 1992, (Beck Electrical Insulation Systems, Hamburg).
Yet another related compound is N-methyl-2-caprolactam, described in the publication K. Wehner et al., Chem. Techn. (8), 1977, pages 445-448, which concerns the use of N-methyl-∈-caprolactam as a selective solvent for gas neutralization, i.e. for the removal of acidic gases, such as CO2 or sulfur-containing acidic gases (e.g., H2S, CH3SH, C2H5SH), from natural gas or synthesis gas.
U.S. Pat. No. 5,326,880, assigned to ISP Investments, teaches asymmetrical polyvinylpyrrolidonyl compounds and their uses as complexing and dispersing agents. Included as Example 4 are two asymmetrical molecules, 1-methyl-3,6-dioxa-1,8-dipyrrolidonyl octane, which has two ether linkages, and N-ethylpyrrolidonyl-pyrrolidonyl polyoxypropylene, which has two or three ether linkages.
U.S. Pat. No. 5,994,562 discloses a process for preparing N-alkenylcarboxamides by dehydration of N-(2-hydroxyalkyl)carboxamides and/or diethers. Dehydration of HEP with undoped catalysts yielded bis-N-ethyl pyrrolidone ether as an unwanted side product at concentrations up to 71%. The '562 patent is directed toward the use of desirable catalysts that reduce the bis-N-ethyl pyrrolidone ether side product to 1% or less.
Despite the development in lactam compounds, there still exists a commercial and industrial need for materials that exhibit excellent solvency and solvent compatibility/miscibility that also provide an improved safety profile. These are the objectives of the present invention, and to describe these lactam compounds, their compositions and uses thereof, especially in various performance chemicals, personal care, and pharmaceutical applications.